Preheat your air fryer to 370 degrees Fahrenheit and spray the basket with nonstick cooking spray.
In a small bowl, combine the butter, parmesan, and garlic powder. Set aside
Place the 2 slices of bread on a cutting board and spread 1 side of each slice with half of the butter. Feel free to build your sandwich here instead of inside the hot air fryer. Flip bread over on cutting board or carefully place butter side down inside your air fryer.
Top with half of the pizza sauce, then half of the mozzarella, all of the pepperoni, and then the remaining half of the mozzarella.
Spread the bare side of the remaining slice of bread with the remaining pizza sauce and arrange the second slice of bread, butter side up, on top of the mozzarella.
Cook the sandwich in your air fryer for about 4 minutes and then gently flip it with a flay spatula. Cook again for an additional 4-6 minutes or until both sides are golden brown.
Once golden brown on both sides and the cheese has melted, remove from the heat and serve. Cut in half if desired. Serve.